JPH1048277A - Polarized light source device and electric field sensor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable polarized light source device incorporated with two light sources which can be used sufficiently without causing any interference even under such a condition that the temperature dependencies of the light sources are allowed with respect to the wavelengths of the light rays emitted from the light sources and emit two kinds of linearly polarized light rays. SOLUTION: A polarized light source device is provided with two light sources 1 and 2 which emit two kinds of linearly polarized light rays perpendicular to each other, temperature control means 21 and 22 which respectively control the temperatures of the light sources 1 and 2, and a photocoupler 9 which synthesizes the linearly polarized light rays from the light sources 1 and 2 so that the planes of polarization of the light rays can become perpendicular to each other. The light sources 1 and 2 are respectively coupled with the photocoupler 9 through relatively short polarization plane maintaining optical fibers 7. The light sources 1 and 2 emit the two kinds of linearly polarized light rays differently from each other while the temperatures of the light sources 1 and 2 are controlled by means of the control means 21 and 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarized light source device for combining and emitting two linearly polarized light beams so that their planes of polarization are perpendicular to each other, and a polarized light source for measuring the electric field strength of electromagnetic waves propagating in space. An electric field sensor using a device, mainly an EMC (Electromagnetic Environment / Electro
The present invention relates to an electric field sensor that is used as a measuring instrument for measuring characteristics of radio waves and electromagnetic noise in the field of magnetic compatibility, and also functions as an antenna that detects a signal radio wave of a specific frequency such as a broadcast radio wave.

[0002]

2. Description of the Related Art Generally, many electric devices such as information devices such as computers, communication devices, FA devices such as robots, and controllers such as automobiles and railways always suffer from adverse effects such as malfunction due to external electromagnetic noise. Known to be at risk.

Therefore, in the recent field of EMC, it is important to accurately measure the external electromagnetic environment, the magnitude of electromagnetic noise that has an adverse effect, or the noise generated by the electric equipment itself.

Conventionally, the following three technical methods have been applied to measure the above-mentioned electromagnetic noise.

[0005] The first method is to receive electromagnetic noise using a normal antenna and guide it to a measuring instrument via a coaxial cable. The second technique is to receive electromagnetic noise using an antenna, detect the received signal, convert the signal into an optical signal, and lead the signal to a measuring instrument via an optical fiber. Further, the third method converts an electric field intensity change of electromagnetic noise into a light intensity change using an optical element configured to change the intensity of transmitted light according to an applied electric field intensity, and The optical fiber is connected between the light source and the photodetector connected to the measuring instrument.

[0006] Of these, the first method is the most common, but there are problems that the electric field distribution may be disturbed due to the presence of an electric cable such as a coaxial cable, or that there is a danger of noise mixing in the middle of the cable. For this reason, the second method and the third method using an optical fiber are now mainstream.

The second method is to amplify a detection signal detected by a diode, convert the signal into an optical signal in addition to a light emitting diode, and guide the signal to an optical detector by an optical fiber. And the need for a battery, there is a problem that a metal part of a certain size is present and the shape becomes large, and there is a drawback that the detection sensitivity of the electric field is low and the response speed is slow.

Further, the third technique uses a crystal having an electro-optical effect as an optical element for converting an electric field intensity into a change in intensity of transmitted light. The element structure is such that a small antenna is connected, the emitted light of the optical fiber is passed through the crystal as a parallel light by a lens, the polarization state is changed by the electric field in the crystal, the light is passed through the analyzer, and then the optical fiber is And a waveguide type element for constituting the above-mentioned optical element by an optical waveguide provided on a crystal.
Normally, the waveguide type device has a detection sensitivity 10 times or more higher than that of the bulk type device. In general, a single crystal of lithium niobate having a high electro-optic constant is used as a substrate crystal for a waveguide type electric field sensor.

FIG. 4 shows a basic configuration of a conventional electric field sensor, and FIG. 5 is a perspective view showing a detailed configuration of a sensor head used in the electric field sensor.

The sensor head 4 has a pair of modulation electrodes 14 at predetermined positions on a lithium niobate single crystal substrate 10 cut out perpendicularly to the c-axis. 15.
A phase shift optical waveguide 12 branched from the incident optical waveguide 11 is coupled to one side and the other side of the pair of modulation electrodes 14, and the output optical waveguide 13 is formed by merging the phase shift optical waveguide 12 on the other side. I have. The polarization maintaining fiber 8 is coupled to the incident end of the incident optical waveguide 11 for incident light.
A single mode fiber 6 is connected to the exit end of the exit optical waveguide 13 for exit light.

In the electric field sensor, light passing through the polarization maintaining fiber 8 from the light source 3 is incident on the sensor head 4 as incident light. In the sensor head 4, after the incident light is incident on the incident optical waveguide 11, the energy is divided by the two phase-shifted optical waveguides 12, and a pair of the modulation electrodes 1 is formed.
4 is transmitted. Here, when an electric field is applied from the outside, a voltage is induced to the pair of modulation electrodes 14 by the antenna 15, and electric field components in the phase-shifted optical waveguide 12 are generated in opposite directions in the depth direction. As a result, the refractive index changes due to the electro-optic effect, and the phase difference between the light waves propagating in the phase shift optical waveguide 12 changes according to the magnitude of the applied electric field. That is, the intensity of the outgoing light emitted to the single mode fiber 6 via the outgoing optical waveguide 13 changes according to the applied electric field intensity, and the change in the light intensity is measured by the photodetector (light receiver) 17. Can measure the intensity of the applied electric field.

In recent years, it has been required to pursue economical efficiency and use a single-mode fiber instead of the polarization-maintaining fiber 8 as the incident optical fiber for the sensor head 4, thereby compensating for an operation disadvantage. Therefore, a configuration in which two linearly polarized light emission light sources are combined is proposed as a light source.

FIG. 6 shows a basic configuration of such another electric field sensor. In this electric field sensor, light sources 1 and 2 emitting two linearly polarized light beams perpendicular to each other are combined and connected to a power supply 20, and a relatively short polarization maintaining fiber 7 for maintaining a polarization plane is used for the light sources 1 and 2. Combiner 9
And the sensor head 4 is provided with a polarizer 16 and the polarizer 16 and the optical coupler 9 are coupled with a single mode fiber 5 so that the incident optical fiber of the sensor head 4 is converted into a single mode fiber. 5 is assumed.

In the case of this configuration, two linearly polarized light beams emitted from the two light sources 1 and 2, which are perpendicular to each other, pass through the polarization plane holding fiber 7 so that their polarization planes are orthogonal to each other by the optical coupler 9. After being combined, the light passes through the single mode fiber 5 while maintaining the state of the polarization planes perpendicular to each other, is polarized by the polarizer 16, and enters the sensor head 4. For this reason, regardless of the state of the single mode fiber 5 at the incident end of the sensor head 4, the polarization plane does not change to the intensity ratio of two linearly polarized light beams perpendicular to each other, and the polarization plane holding fiber is substantially used. The same effect can be obtained.

The light sources 1 and 2 and the optical coupler 9 here
And a pair of polarization maintaining fibers 7 connected between them.
Means that the emitted light is combined and emitted so that the planes of polarization of the two linearly polarized light beams are perpendicular to each other, and may be collectively referred to as a polarized light source device.

Light sources 1 and 2 used in such an electric field sensor
Since semiconductor lasers are required to have high reliability such as obtaining a constant output in a predetermined wavelength band and ensuring a long life, semiconductor-pumped solid-state lasers are used. Semiconductor-pumped solid-state lasers have attracted attention as light sources that satisfy these conditions.

[0017]

In the case of the electric field sensor shown in FIG. 6, the semiconductor excitation fixed laser is used as the two light sources in the polarized light source device. It is known that it fluctuates depending on the temperature of the light source.

Such a variation in the wavelength of the emitted light is not significant in the case of the electric field sensor using the polarization maintaining fiber shown in FIGS. When two light sources are used, there is a problem of mutual interference between the two emitted lights, so that the electric field sensor may not perform its original function. That is, if the wavelengths of the two light sources and their temperature dependencies are equal, the incident lights of the sensor head always interfere with each other, or the wavelengths are equal in the drive temperature range even if the temperature dependencies of the wavelengths of the two light sources are different. If so, interference will occur at that temperature as well. Therefore, in such a case, the reliability of the electric field sensor is reduced.
A semiconductor-excitation fixed laser cannot be used as a light source for the sensor head.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and its technical problem is that interference does not occur even under conditions that allow the light source temperature dependence on the wavelength of the light emitted from the light source. Another object of the present invention is to provide a polarized light source device including a light source that emits two linearly polarized lights with high reliability that can be sufficiently used, and an electric field sensor using the same.

[0020]

According to the present invention, there are provided two light sources for emitting two linearly polarized light beams perpendicular to each other, and an optical coupler for combining the two linearly polarized light beams so that their polarization planes are perpendicular to each other. In the polarized light source device provided with the above, a polarized light source device is obtained in which the two light sources emit the two linearly polarized lights with different wavelengths.

Further, according to the present invention, in the above-mentioned polarized light source device, a polarized light source device in which at least one of the two light sources has a temperature control means can be obtained.

Further, according to the present invention, in any of the above-mentioned polarized light source devices, a polarized light source device in which the two light sources are semiconductor-excited solid-state lasers is obtained.

On the other hand, according to the present invention, any one of the above polarized light source devices, an antenna, a sensor head connected to the antenna, an incident optical fiber as an input light transmission path in the sensor head, An electric field sensor including an output optical fiber as an output optical transmission line and a photodetector coupled to the output optical fiber is obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The polarized light source device of the present invention and an electric field sensor using the same will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of a polarized light source device according to an embodiment of the present invention. This polarized light source device has the same external appearance as the local configuration of the electric field sensor shown in FIG. It has become.

That is, in this polarized light source device, two light sources 1 and 2 that emit two linearly polarized lights perpendicular to each other and two linearly polarized lights from these light sources 1 and 2 are arranged so that the planes of polarization are perpendicular to each other. An optical coupler 9 is provided, and the light source 1 and the optical coupler 9 and the light source 2 and the optical coupler 9 are respectively coupled by a relatively short polarization maintaining fiber 7, Here, the light sources 1 and 2 emit the two linearly polarized lights with different wavelengths.
The light sources 1 and 2 are semiconductor-pumped YAG lasers, and the wavelength of the emitted light is 1.3190 μm at a temperature of 23 ° C., respectively.
1.3195 μm, and the emitted light intensities are almost equal. The temperature dependence of the wavelengths of these light sources 1 and 2 is selected to be 6 × 10 ⁻⁶ μm / ° C. so that the wavelengths do not coincide with each other in the operating temperature range (−20 to + 60 ° C.).

In this polarized light source device, the mutually perpendicular linearly polarized lights emitted from the light sources 1 and 2 are maintained in their respective states via the polarization plane maintaining fiber 7, and the optical coupler 9.
Then, the polarization planes are coupled so as to be perpendicular to each other, and thereafter, they propagate in the single mode fiber 5 while maintaining the polarization planes perpendicular to each other.

An electric field sensor equipped with this polarized light source device as a light source has the same configuration as the conventional electric field sensor shown in FIG. However, in the case of this electric field sensor, the light sources 1 and 2 emit two linearly polarized lights having different wavelengths, which are guaranteed not to interfere in the operating temperature range, as the emitted light.
2, the original function is exhibited with sufficient reliability. Further, in this electric field sensor, even if the single mode fiber 5 coupled to the output side of the polarized light source device (optical coupler 9) is sufficiently long, the polarization planes of the two linearly polarized light remain perpendicular to each other after passing through the single mode fiber. Therefore, the same effect as in the case where the polarization maintaining fiber 8 described with reference to FIGS. 4 and 5 is used can be obtained.

FIG. 2 shows a basic configuration of a polarized light source device according to another embodiment of the present invention.

This polarized light source device is different from the polarized light source device of one embodiment in that the light sources 1 and 2 are provided with temperature control means 21 and 22, respectively, in appearance. Each of the light sources 1 and 2 is a semiconductor-excited YAG laser, and the temperature of each is controlled by temperature control means 21 and 22. The wavelengths of the light emitted from the light sources 1 and 2 are 1.3190 μm and 1.3193 μm at a temperature of 23 ° C., and the temperature dependence of the wavelength is 6 × 10 ⁻⁶ μm / ° C., respectively. The intensity of the emitted light is almost equal.

In this polarized light source device, if the temperature control by the temperature control means 21 and 22 is not performed, there is a possibility that the wavelengths coincide during operation, and in this case, mutual interference occurs. Therefore, the temperature control means 21,
By controlling the temperatures of the light sources 1 and 2 with the use of the light source 22, such a situation is avoided, and emitted light of a certain wavelength can be obtained. Temperature control means 21, 22
May be a thermoelectric temperature element such as a Peltier element, or a heating and cooling storage using a heat exchange medium.

FIG. 3 shows the basic configuration of an electric field sensor equipped with this polarized light source device as a light source.

In this electric field sensor, the configuration other than the polarized light source device is the same as that of the conventional electric field sensor shown in FIG. However, also in this electric field sensor, the temperatures of the light sources 1 and 2 that emit two linearly polarized lights having different wavelengths as emission light are controlled by the temperature control means 21 and 22 so as not to interfere in the operating temperature range. As in the case of the electric field sensor provided with the polarized light source device of the embodiment, the original function is exhibited with sufficient reliability. In particular, the electric field sensor here is a light source 1 by the temperature control means 21 and 22.
Since the second temperature control is performed, the method is suitable for measurement and the like that require sufficient reliability even in a severe temperature environment.

It is to be noted that the configuration of the polarized light source device according to the other embodiment shown in FIG. 2 described above is improved, and a configuration (not shown) for controlling the temperature of only one of the light sources 1 and 2 similarly causes interference. Since it can be avoided, the same effect can be obtained even if an electric field sensor including such a polarized light source device as a light source is configured.

[0035]

As described above, according to the polarized light source device of the present invention, the light source that emits two linearly polarized light beams that are perpendicular to each other emits light having two different linearly polarized light wavelengths. Since the temperature control means is provided in any one of the light sources, even if the light source temperature dependence on the wavelength of the light emitted from the light source is allowed, no interference occurs, and a highly reliable electric field using the polarized light source device is used. A sensor can be realized. In particular, in this electric field sensor, even if the single mode fiber coupled to the exit side of the polarized light source device (optical coupler) is sufficiently long, the polarization planes of the two linearly polarized light beams are kept perpendicular to each other after passing through the single mode fiber. As a result, the same performance as in the case where the conventional polarization maintaining fiber is used is ensured.

[Brief description of the drawings]

FIG. 1 shows a basic configuration of a polarized light source device according to one embodiment of the present invention.

FIG. 2 shows a basic configuration of a polarized light source device according to another embodiment of the present invention.

FIG. 3 shows a basic configuration of an electric field sensor provided with the polarized light source device shown in FIG. 2 as a light source.

FIG. 4 shows a basic configuration of a conventional electric field sensor.

FIG. 5 is a perspective view showing a detailed configuration of a sensor head used in the electric field sensor shown in FIG.

6 shows a basic configuration of another electric field sensor obtained by improving the electric field sensor shown in FIG.

[Explanation of symbols]

 1, 2, 3 Light source 4 Sensor head 5, 6 Single mode fiber 5 7, 8 Polarization maintaining fiber 9 Optical coupler 10 Lithium niobate single crystal substrate 11 Incident optical waveguide 12 Phase shift optical waveguide 13 Emitting optical waveguide 14 Modulation Electrode 15 Antenna 16 Polarizer 17 Photodetector 20 Power supply 21, 22 Temperature control means

Claims (4)

[Claims] 1. A polarized light source device comprising: two light sources that emit two linearly polarized light beams perpendicular to each other; and an optical coupler that combines the two linearly polarized light beams so that their polarization planes are perpendicular to each other. A polarized light source device, wherein the two light sources emit the two linearly polarized lights with different wavelengths. 2. The polarized light source device according to claim 1,
At least one of the two light sources has a temperature control means. 3. The polarized light source device according to claim 1, wherein said two light sources are semiconductor-pumped solid-state lasers. 4. The polarized light source device according to claim 1, an antenna, a sensor head connected to the antenna, an incident optical fiber as an input light transmission path in the sensor head, and the sensor. An electric field sensor comprising: an output optical fiber as an output light transmission path in a head; and a photodetector coupled to the output optical fiber.